The invention relates in general to electromagnetically operated actuators for controlling fluid flow and in particular to varying the dynamic response of such actuators.
Various components such as servo-valves, pressure regulators and fuel injectors may be used in both open and closed loop dynamic control systems for controlling fluid flow. It may be necessary to change the response characteristic of such components to fine tune the component within the system or to alter the overall system characteristic.
Electromagnetically operated actuators for controlling fluid flow generally include an armature disposed in a sleeve and actuated by an electric coil. The actuators control the amount of fluid flow at different pressures and are designed to operate within a certain range. Various conditions, such as high pressure and temperature, may push the limits of the actuator""s operating range. Conditions such as high pressure and temperature change the operating fluid viscosity dramatically. Such changes in fluid viscosity may force the actuator to become unstable and oscillate. Thus, a need exists for an actuator which remains stable under varying conditions of pressure and temperature.
The present invention provides an apparatus comprising an armature having at least one groove formed on an exterior surface thereof; a sleeve, the armature being movably disposed in the sleeve; and a spring member disposed in the at least one groove in the armature and in sliding contact with the sleeve wherein the spring member exerts a radially outwardly directed spring force against the sleeve.
Another aspect of the invention is a method of stabilizing an electromagnetically operated actuator comprising providing an armature having at least one groove formed on an exterior surface thereof; providing a sleeve wherein the armature is movably disposed in the sleeve; and disposing a spring member in the at least one groove in the armature and in sliding contact with the sleeve whereby the spring member exerts a radially outwardly directed spring force against the sleeve.
Yet another embodiment of the invention is an apparatus comprising a sleeve having at least one groove formed on an interior surface thereof; an armature, the armature being movably disposed in the sleeve; and a spring member disposed in the at least one groove in the sleeve and in sliding contact with the armature wherein the spring member exerts a friction force against the armature.
Another aspect of the invention is an apparatus comprising an armature having at least one radial opening formed therein; a sleeve, the armature being movably disposed in the sleeve; a spring disposed in the at least one radial opening in the armature; and a bearing member disposed on one end of the spring and in sliding contact with the sleeve wherein the bearing member exerts a radially outwardly directed force against the sleeve.